Bitumen dispersions and process of making same



Patented June 20, 1939 UNITED STATES PATENT OFFICE BITUMEN DISPERSIONSAND PROCESS OF MAKING SAME setts N Drawing.

Application July 31, 1935, Serial No. 33,963. In Great Britain August 2,1934 9 Claims.

The present invention concerns a process for the manufacture of bitumendispersions of a relatively high stability so that, when applied inroadmaking, they are suitable for being mixed with very fine mineralaggregates.

Bitumen dispersions of high stability have hitherto been prepared inseveral ways, for in stance with the aid of proteins, carbohydrates orthe like, or with inorganic colloidal or finely divided solidemulsifiers.

Protein or carbohydrate emulsifiers or stabilizers may give dispersionsin which the bitumen is dispersed to a sufficiently fine particle size,but these dispersions are often difficult to handleon account of thetendency on the part of the emulsiher to form stiff gels or highlyviscous solutionsand also as a rule they cannot be satisfactorily storedunder normal conditions because the said emulsifiers are subject toputrefaction.

In organic emulsifiers, such 'as colloidal clay or the ges of thehydroxides of multivalent metals, give bitumen dispersions which areusually very coarse, compared with normal dispersions made with soapsolutions; moreover they are usually of a thick pasty consistency orelse thixctropic. The dispersions of this type therefore cannot behandled in the same way as normal road dispersions, which are fluid andcan easily be pumped and sprayed. Moreover, the very coarse degree ofdispersion of the bitumen renders them to a large extent unsatisfactory,since the dispersed bitumen particles are comparable in size to orlarger than the particles of the fine mineral aggregate around whichthey should be capable of forming a continuous film of bitumen.

The emulsifiers which have been mentioned above are all insoluble inbitumen, even when they are dry, and the dried film from the dispersioncontains these emulsifiers as a structure which immobilises the film andrenders it non-tacky.

Each of the present known types of stable bitumen dispersions thereforeshows disadvantages under some or all of the following headings:

1, putrefaction; 2, abnormal fiow properties; 3,

5 coarse dispersion; 4 insolubility of the emulsifier in the bitumen.

The bitumen dispersions of a relatively high stability according to theinvention, which are prepared with a neutral or alkaline, aqueoussolution of an alkali soap of solid rosin, are characterized by thepresence therein of a suitable quantity of calcium or such likerosinate.

According to the invention the preferred process for the manufacture ofbitumen dispersions of high stability comprises incorporating into thebitumen a suitable quantity of a specially prepared calcium rosinate andthereupon dispersing the bitumen thus treated in a neutral or alkaline,aqueous solution of an alkali (potassium or sodium) soap of solid rosin.Bitumen dispersions pre- 5 pared in accordance with the above arereferred to hereinafter as Type I.

According to the invention also the said bitu men dispersions can bestabilised further by the addition of a calcium chloride solutionpreferably in an amount chemically equivalent to the amount of alkaliresin soap emulsifier used. In a similar way also other normallycoagulative electrolyte solutions capable of acting upon the alkaliresin soap emuisifier, such as aluminium chloride, may be used insteadof calcium chloride. Bitumen dispersions prepared in this way arereferred to hereinafter as Type II.

Calcium rosinate may be prepared by heating a mixture of solid rosin andquick or hydrated lime, using sufiicient lime to neutralise the acids ofthe rosin. Heating is continued until the material on cooling is foundto be free from uncombined lime. Since, however, certain commercialgrades of calcium rosinate, or lime-hardened rosin, may not besatisfactory for the purposes of the invention, care should be taken toselect the proper type of solid rosin which yields satisfactory resultswith respect to the high stability desired in the bitumen dispersion. Ingeneral wood rosins have been found to suit best the purposes of theinvention, although in certain cases the Wood rosin may be substitutedby other types of rosin, either for preparing the alkali resin soap usedas the emulsifier, or for preparing the calcium rosinate, but preferablynot for both purposes.

The process, which gave successful results, was carried out with aparticular type of solid rosin which is obtained as a residue in thefurfural extraction of crude wood rosin. More particularly the solidrosin employed herein is one sold under the designation B rosin which isa waste product resulting from the process used in decolorizing rosins.For example, so-called FF Rosin (ruby red in color) is decolorized bybeing first dissolved in gasoline; a sufficient quantity of furfural isthen added. This forms a two liquid layer system in which the furfurallayer acts as a selective solvent on the unsaponifiables and coloringbodies 50 in the original FF Rosin used. After proper treatment thefurfural layer is separated and distilled to recover the furfural andthe residue remaining is the so-called B Rosin. This B Rosin residuecontains most of unsaponifiables from the original rosin, and most ofthe coloring bodies, as well as a good proportion of the rosin acids.

For example, the so-called FF Rosin shows an analysis substantially asfollows:

Percent Unsaponifiables 5 Coloring bodies less than 1 Gasolineinsolubles 8 Rosin (as abietic acid) 94 After treatment such as abovedescribed for decolorizing the same, the B Rosin separated from thefurfural layer would have an approximate analysis as follows:

Percent Unsaponifiables 10 to 20 Coloring bodies lto 2 Gasolineinsolubles 60 Rosin (as abietic acid) '79 to 88 The gasoline layer isalso distilled and yields a yellow rosin containing a small percentageof unsaponifiables, and a very small amount of coloring bodies.

It is thus seen that the selective solvent action distributes the rosinbetween the two liquid layers and brings the main portion of theunsaponifiables and coloring bodies into the furfural layer. We Wish tostate, however, that the process according to the invention is notlimited to the use of that particular brand of resin, it being alsoapplicable with other grades of rosin of the same character and origincapable of producing similar stability in the bitumen dispersionsprepared with the aid thereof.

The calcium rosinate prepared in the above-described manner from theabove mentioned B grade rosin has a melting point of about 135 C. and isnot readily dissolved in bitumen or fuel oil at a temperature of 140C.,'which is normally the highest convenient working temperature. If,however, the calcium rosinate is fiuxed with a further proportion ofrosin or if less lime than is required to neutralise the rosin is usedin the preparation of the rosinate, a product is obtained which shows alower melting point and is more easily dissolved; the greater thequantity of excess rosin present, the lower the melting point. Thelatter calcium rosinate preparations, which in the present instance arereferred to as lime-hardened rosin, may be dissolved directly in bitumenor, for conveniences sake, may be first dissolved in fuel oil to give asolution which is used to fiux a harder bitumen to a blend of thedesired penetration.

In a modification of the above process a solution of lime-hardened rosinin fuel oil may be made from a fuel oil solution of rosin and sufiicientlime to neutralise part of the rosin, by heating the mixture until it isseen to be homogeneous on cooling. As already stated, the fuel oilsolution may then be used to flux a hard bitumen.

In an alternative embodiment of the invention a bitumen dispersion ofthe same stable type may be prepared by adding an aqueous suspension ofcalcium rosinate to a bitumen dispersion prepared by dispersing thebitumen in a solution of the potassium or sodium soap of solid rosin.The aqueous suspension of calcium rosinate is prepared by partiallydecomposing a solution of the potassium or sodium soap of solid rosinwith an aqueous solution of calcium chloride.

A further alternative method of carrying out the invention is to add toa bitumen dispersion prepared by means of an alkali soap of solid rosina quantity of a solution of salt of a metal forming an insolublerosinate by double decomposition with the alkali rosinate, the saidquantity and concentration of metal salt solution being preferably suchthat the alkali rosinate is just completely decomposed. In carrying outthis form of the invention it is necessary to choose such a dilution ofthe original emulsion, and such concentration of the added metal saltsolution that at the temperature of addition there is no 00-- agulationof bitumen. Generally speaking, more concentrated initial emulsion andmore concentrated metal salt solution may be used at lower temperatures.There is in many cases a limiting temperature above which the additioncannot be made without producing coagulation. This temperature must befound by experiment in any particular case.

The bitumen dispersions prepared according to the invention present thefollowing advantages:

Neither the soap emulsifier nor the calcium rosinate introduced into thebitumen in this process are subject to putrefaction.

The bitumen dispersion referred to as Type I is indistinguishable asregards normal characteristics, such as microscopic appearance, fiow andstorage properties, from a normal good quality dispersion for use inroad-making made with soap solution as emulsifier.

The stability of this Type I dispersion to mixing with fine mineralaggregates is, however, very much greater than that of normal roaddispersions and is similar to that of dispersions made with protein,carbohydrate or inorganic emulsifiers. The Type I dispersion is alsostable to the addition of unlimited quantities of solutions of moderateconcentration of various electrolytes, eX- cept mineral acids; however,on diluting the dispersion sufficiently with water it becomes stablealso to mineral acids.

The bitumen dispersion referred to as Type II, which is made from adispersion of Type I by the addition of sufficient calcium chloridesolution to decompose the resin soap of the emulsifier, is distinguishedfrom that of Type I by initially showing thixotropic properties. Onstanding for a short time, however, the dispersion changes to a fluidsystem in which aggregates of particles, in the form of clots or clumps,are suspended in an aqueous medium. These aggregates of particles arereadily redispersed and the dispersion is entirely suitable to be mixedwith fine mineral aggregates. This Type II dispersion is of even greaterstability than that of Type I and is stable, either as such or afterdilution with water, to the addition of unlimited quantities ofsolutions of electrolytes, including mineral acids, of highconcentrations.

Since for either type of dispersion the solubility of the calciumrosinate in the bitumen is essential to the process, this emulsifiercannot form the structure in the dried film, which is a disadvantage ofstable dispersions of other types.

EXAMPLE Type I Lime-hardened rosin is prepared by heating the followingmixture at 140 C. until homogeneous on cooling:

Parts Solid rosin (furfural extracted type) 100 Hydrated lime 3.75

This material is dissolved at 140 C. in an equal weight of fuel oilhaving a viscosity of 6000 seconds tested by the method known as RedwoodI.

According to the usual viscosity conversion tables,

this viscosity corresponds, in terms of kinematic viscosity, to about1464 centistokes or, with regard to the average specific weight of thefuel oil, about 1400 centipoises. 4 parts of the solution are added to100 parts of 200 penetration bitumen and the mixture is dispersed in aneutral potassium rosinate solution of N/20 concentration, in the normalway, to give a dispersion of 57% bitumen content. The dispersion thusprepared is of Type I.

Type II Sufiicient 10% calcium chloride solution is added to the colddispersion of Type I in order to decompose the soap of the emulsifier,which in a typical case was 1.18 part of said solution to 100 parts ofbitumen dispersion.

Having now particularly described and ascertained the nature of our saidinvention and in what manner the same is to be performed, We declarethat what we claim is:

l. A dispersion of bitumen in water of relatively high stabilitysuitable for road making, said dispersion containing, as a dispersingagent, a Water soluble alkali metal soap of a solid rosin andcontaining, as a stabilizing agent, a calcium salt of a solid rosinwhereby said dispersion will be characterized by freedom fromputrefaction and abnormal flow properties and by stability to mixingwith fine mineral aggregate and with solutions of moderateconcentrations of electrolytes other than mineral acids.

2. A dispersion of bitumen in water of relatively high stabilitysuitable for road making, said dispersion containing, as a dispersingagent, a water soluble alkali metal soap of a solid rosin andcontaining, as a stabilizing agent, a calcium salt of a solidwood-rosin, whereby said dispersion will be characterized by freedomfrom putrefaction and abnormal flow properties and by stability tomixing with fine mineral aggregate and with solutions of moderateconcentrations of electrolytes other than mineral acids.

3. A dispersion of bitumen in water of relatively high stabilitysuitable for road making, said dispersion containing a calcium salt of asolid rosin and containing also the reaction product of a Water solublealkali metal soap of a solid rosin and a water soluble salt of amultivalent metal, whereby said dispersion will be characterized byfreedom from putrefaction and abnormal flow properties and by stabilityto mixing with fine mineral aggregate and with solutions ofelectrolytes.

4. A dispersion of bitumen in water of relatively high stabilitysuitable for road making, said dispersion containing a calcium salt of asolid wood-rosin and containing also the reaction product of a watersoluble alkali metal soap of a solid rosin and a water soluble salt of amultivalent metal, whereby said dispersion will be characterized byfreedom from putrefaction and abnormal fiow properties and by stabilityto mixing with fine mineral aggregate and With solutions ofelectrolytes.

5. A process for the manufacture of aqueous dispersions of bitumen ofrelatively high stability, which comprises dispersing the bitumen,admixed with a calcium salt of a solid rosin, in an aqueous solution ofa water soluble alkali metal soap of a solid rosin.

6. A process for the manufacture of aqueous dispersions of bitumen ofrelatively high stability, which comprises dispersing the bitumen,admixed with calcium salt of a solid wood rosin, in an aqueous solutionof a water soluble alkali metal soap of a solid rosin.

7. A process for the manufacture of aqueous dispersions of bitumen ofrelatively high stability, which comprises dispersing the bitumen,admixed with calcium salt of a solid rosin, in an aqueous solution of awater soluble alkali metal soap of a solid rosin and then adding, tolthe said dispersion a Water soluble salt of a multivalent metal in anamount substantially chemically equivalent to the amount of said watersoluble alkali metal soap of solid rosin.

8. A process for the manufacture of aqueous dispersions of bitumen ofrelatively high stability, which comprises first dispersing the bitumenin an aqueous solution of a water soluble alkali metal soap of a solidrosin, and then adding to such dispersion an aqueous suspension ofcalcium rosinate.

9. A process for the manufacture of aqueous dispersions of bitumen ofrelatively high stability, which comprises first dispersing the bitumenin an aqueous solution of water soluble alkali metal soap of a solidrosin, and then adding a water soluble salt of a multivalent metal tothe said bitumen dispersion, the quantity and concentration of saidWater soluble salt of a multivalent metal being regulated so as to justcompletely decompose the said alkali soap of solid rosin.

LEONARD GOWEN GABRIEL.

JOHN FREDERIC THOMAS BLOTT.

